/Engine/Source/Runtime/Foliage/Public/InstancedFoliageActor.h
Will return all the foliage type used by currently selected instances.
[TMap](API\Runtime\Core\Containers\TMap)< [UFoliageType](API\Runtime\Foliage\UFoliageType) *, [FFoliageInfo](API\Runtime\Foliage\FFoliageInfo) * > GetSelectedInstancesFoliageType()